This invention is directed generally to the field of spindle motors as used in disc drives, and more particularly to an improved structure and method for assembly of a spindle motor.
Winchester disc drives are being used in computers to store increasingly large amounts of information while the cost of such storage is dropping dramatically. The typical Winchester disc drive is a system with a limited number of mechanical parts, including a spindle motor which mounts one or more discs for constant speed rotation, and an actuator carrying a transducer at one end and a voice coil motor at the other and operable in response to commands to the voice coil motor to position the transducer over a selected track to read and write data.
As one of the most expensive elements of a disc drive, as well as being one of the largest and most mechanically complex, many design efforts are intended to minimize the cost and increase the ease of assembly of the spindle motor. This particular invention is especially directed to improving spindle motor design and ease of assembly thereof, specifically in a spindle motor which incorporates a hollow shaft through which the wires to be connected to the stator are fed. It is apparent that it is essential to provide a reliable means for connecting these wires to the stator without taking additional axial space which could be used for larger stator and magnet. However, the assembly process as currently known can be complex, requiring spliced connections or the like. This could easily lead to loose wires on the stator which could result in a need to rework the motor or failure of the motor in its application. Further, the current assembly method which requires that the wires be fed through the hollow shaft and then soldered to lead wires extended from the stator is time consuming and costly. The time needed for testing the motor is also unduly lengthened.
Therefore, it is an object of the present invention to provide an improved spindle motor design for use in a disc drive.
A related objective of the invention is to provide a simplified spindle motor design which is subject to a simplified assembly process, eliminating splicing of connections and loose.wires frequently associated with the stator assembly in the prior art.
Another related invention is to provide a stator design which can be easily tested as a unit for resistance, inductance, and continuity before assembly into the motor.
Another objective of the invention is to eliminate or dimminish the need for axial space reserved for making connections to the stator leads.
Yet a further objective of the invention is to provide an assembly process which simplifies the insertion of the lead wires through the hollow shaft of the motor to be soldered to the lead wires from the spindle motor stator.
These and other objectives of the invention are provided by a spindle motor incorporating a hollow shaft and a prewound stator incorporating an interconnect ring which is incorporated in and attached to one end of the stator assembly. The interconnect ring is preferably a printed circuit or flexible printed circuit which is fastened to an end of the stator stack before the stator has been wound. This interconnect ring is bonded to the stator stack before the coils are wound, and the start and finish of each phase winding is terminated to the interconnect ring. Once the stator is assembled onto the shaft, connector wires can be fed up through the shaft and terminated at the interconnect ring. Traces on the interconnect ring join the wires to the proper phases and to the commons to control motor operation.
The result of adopting this structure is to provide a motor shaft and stator assembly which is more easily and reliably assembled, wound and tested.